`dct` prefix should be `dcterms` in the LD Context

[jmcanterafonseca-iota]

At https://eclipse-dataspace-protocol-base.github.io/DataspaceProtocol/2025-1/message/schema/dspace.jsonld

there is a prefix term defined for DC Terms as

"dct":	"http://purl.org/dc/terms/" 

I propose to change it to dcterms to match the prefix definition at the dcatv3 LD Context, see https://www.w3.org/ns/dcat3.jsonld

Rationale:
1/ For consistency reasons as it happens with other prefixes, namely odrl.

2/ That way it will be easier that a Dataset expressed using the LD Context of DCAT to be seamlessly compacted usingthe DS Protocol LD Context. Example:

If someone supplies a dataset as

{
   "@context":  "https://www.w3.org/ns/dcat3.jsonld",
  "@type": "dcat:Dataset",
  "dcterms:type": "https://schema.org/Organization"
  ..... 
}

It can be easily compacted using

JsonLdProcessor.compact(originalDataset, ["https://w3id.org/dspace/2025/1/context.jsonld"])

resulting in:

{
   "@context":  "https://w3id.org/dspace/2025/1/context.jsonld",
  "@type": "Dataset",
  "dcterms:type": "https://schema.org/Organization"
}

instead of

{
  "@context":  "https://w3id.org/dspace/2025/1/context.jsonld",
  "@type": "Dataset",
  "dct:type": "https://schema.org/Organization"
}

which can clearly confuse developers and makes lives harder for implementers.